The present disclosure relates to a developing device for supplying a developer to an image carrier and an electro-photographic image forming apparatus including the developing device.
In an image forming apparatus of the electro-photographic type, an electrostatic latent image is formed by directing light to a circumferential surface of an image carrier (photosensitive drum) based on image information read from a document image or on image information transmitted from external devices such as a computer and the like, and a toner image is formed by supplying toners from a developing device to the electrostatic latent image, thereafter, the toner image is transferred onto a paper sheet. The paper sheet after the transfer process undergoes a toner-image fixing process, and then is ejected to outside.
And, as the developing method that uses dry toners in an image forming apparatus that uses an electro-photographic process, a developing method is proposed, in which when moving a developer, by using a magnetic roller (toner supplying roller), onto a developing roller disposed not to contact a photoreceptor (image carrier), only non-magnetic toners are transferred onto the developing roller to form a toner thin layer with the magnetic carriers left on the magnetic roller; and toners are made to adhere to an electrostatic latent image on the photoreceptor by using an a.c. electric field at an opposing region (developing region) between the developing roller and the photoreceptor.
In the meantime, in recent years, in an image forming apparatus, because of a transition to color printing and high speed processing, an apparatus structure is becoming complicated, and in order to be compatible with the high speed processing, it is inevitable to rotate a toner stir member in a developing device at a high speed in particular, in the above developing method that uses a two-component developer containing magnetic carriers and toners, a magnetic roller for carrying the developer and a developing roller for carrying the toners only, at an opposing portion between the developing roller and the magnetic roller, only the toners are carried onto the developing roller by a magnetic brush formed on the magnetic roller, and further, toners that are left unused for the developing are peeled off the developing roller. Accordingly, floating toners are liable to occur near the opposing portion between the developing roller and the magnetic roller, and if the floating toners accumulate around a bristle cut blade (regulation blade) and the accumulating toners aggregate and adhere to the developing roller, there is a risk that toner dropping could occur and cause an image defect.
To solve the above problems, a developing device is known, which at a wall portion that opposes a developing roller between a regulation blade and a developing region, includes: a flexible sheet member that composes a portion of an inner wall surface of the wall portion and is vibratile in a direction perpendicular to the inner wall surface; and an ellipsoidal roller that moves the sheet member.
Besides, a developing device is known, which includes a vibration mechanism that gives an acceleration in a direction in which toners adhering to a vessel wall of the developing device are made to fall into the vessel.
In the developing device that includes the flexible sheet member and the ellipsoidal roller that moves the sheet member, the sheet member is moved by using rotation of the ellipsoidal roller, whereby the toners accumulating on the sheet member are shaken off. Besides, in the developing device which includes the vibration mechanism that gives an acceleration to the vessel wall of the developing device, the developing device itself is vibrated by the vibration mechanism, whereby the toners adhering to the developer vessel are shaken off. However, the structure which moves the flexible sheet member by using the ellipsoidal roller additionally needs a motor for rotating the ellipsoidal roller; and also the structure which moves the developer vessel itself by using the vibration mechanism additionally needs a lever and an actuator, an electromagnetic solenoid and the like which compose the vibration mechanism, accordingly, there are problems that the cost of the developing devices increases and the structures become complicated.